1. Field of the Invention
The present invention relates to a method, system, and computer program product for a Maintenance Optimization Model (MOM), and more specifically to a method, system, and computer program product including a MOM driving design of a product, such as an aircraft, towards minimum operating cost while ensuring optimum availability for an end-user, such as an airline operating the aircraft.
2. Description of the Related Art
Design of certain products, such as an aircraft, has shifted its focus from the traditional design for performance to designing for affordability and quality. This paradigm shift calls for solutions that are beyond historical databases and demands the consideration of all aspects of the product's life cycle. An approach based on relations among reliability, availability, maintainability, and life cycle cost requirements can be more appropriate (see Jean-Jacques Dindeleux, Jacques J. Durand, Alstom Transportation Inc., and Stephanie Delsaut, Ligeron S. A. Consulting, Design integrated reliability studies according to requirements analysis and return of experience, RAMS Symposium, January 2005, incorporated by reference herein).
Life Cycle Cost (LCC) management has gained paramount importance in decision-making processes for new technology, design, and procurements (see Scanlan, James, Hill, Terry, Marsh, Rob, Bru, Christophe, Dunkley, Martin and Cleevely, Paul (2002) Cost modeling for aircraft design optimization. Journal of Engineering Design, 13, (3), 261-269, incorporated by reference herein). Determining the optimum repair and overhaul strategy to minimize LCC is a problem receiving increased attention (see (L. H. Crow, Methods for Reducing the Cost to Maintain a Fleet of Repairable Systems, RAMS Symposium, 2003, pp. 392-399, incorporated by reference herein) and (Wallace R. Blischke and D. N. Prabhakar Murthy, Case study in reliability and maintenance, 2003).
Product evaluation, for example in the aircraft industry, has been traditionally based primarily on an economical figure: the Direct Operating Cost (DOC). DOC combines parameters like reliability and maintainability by calculating their economical implications. Although it is debated which cost elements do belong in a DOC calculation, and which don't, it is generally admitted that DOC includes those cost elements, which depend on the aircraft itself. Indirect Operating Costs (IOC), in contrast, depend on the way an airline is run (see Van Bondergraven, G. W.: Commercial Aircraft DOC Methods (AIAA/AHS/ASEE Aircraft Design, Systems and Operations Conference, Dayton, 17.-19. Sep. 1990), American Institute of Aeronautics and Astronautics, 1990 (Paper AIAA-90-3224-CP), incorporated by reference herein).
Aircraft DOC methods have been discussed e.g. by:                The Air Transport Association of America, 1967 [ATA 67] (Air Transport association of America: Standard Method of Estimating Comparative Direct Operating Costs of Turbine Powered Transport Airplanes, Washington D.C.: ATA, 1967);        The Association of European Airlines, 1989 [AEA 89a] (Association of European Airlines: Short-Medium Range Aircraft AEA Requirements, Briissel: AEA, 1989 (G(T)5656)), [AEA 89b] (Association of European Airlines: Long Range Aircraft AEA Requirements, Brussel: AEA, 1989 (G(T)5655));        Airbus Industrie [Airbus 88] (Airbus Industrie: Airbus Project D.O.C. method, Toulouse, 1988 (AI/TA-P812.076/88 ISS.1));        Lufthansa [LUFTHANSA 82] (Lufthansa: DLH Method 1982 for Definition of the Performance and Direct Operating Costs of Commercial Fixed Wing Aircraft, Lufthansa, Hamburg, 1982); and        NASA [NASA 05] (National Aeronautics and Space Administration, Franklin D. Harris: An Economic Model of U.S. Airline Operating Expenses, NASA Ames Research Center under Grant NAG-2-1597, (NASA/CR-2005-213476)).        
Unfortunately these methods cannot be taken “as is” for an aircraft product evaluation. In contrast to traditional DOC methods, a DOC method on a system level preferably incorporates many system-specific parameters. Therefore, a method called DOCsys has been developed (see D. Scholz: DOCsys, A Method to Evaluate Aircraft Systems. Workshop: DGLR Fachausschuβ S2, Luftfahrtsysteme in München. 1998, incorporated herein by reference) which follows the principles of traditional aircraft DOC methods as closely as possible, while taking aircraft system peculiarities into account. DOCsys is similar to the Cost of Ownership (COO) methods previously presented (see Honeywell Inc., Commercial Flight Systems Group: Cost of Ownership Analysis, Phoenix, 1991; and see Dechow, M.; Herold, H.: CONSUL, Berechnungsprogramm für die Ermittlung des Cost of Owership für Systeme und LRUs, Version 1.1, Deutsche Aerospace Airbus, Hamburg, 1994 (EZ32)). These COO methods, however, consider primarily single parts Line Replaceable Units (LRUs) and do not support as much the evaluation of systems and sub-systems. In addition, the term “Cost of Ownership” is also used for the costs resulting in just owning an aircraft, system, or sub-system, without using it (see Odell, T. T.: Boeing HSCT OpCost Methodology, Seattle: Boeing Commercial Airplane Group, 1993 (6-1442-MES-HSCT-002-93)). The term Direct Operating Cost avoids these misinterpretations and DOCsys has several advantages over an evaluation based on separate criteria or based on COO methods. The cost elements considered in the DOCsys method of Scholz are:                fuel costs caused by the system;        Direct Maintenance Cost (DMC) caused by the system;        capital costs caused by necessary spare parts on stock (spare holding costs); and        delay, cancellation, and diversion costs caused by an aircraft system.        
However, in DOCSYS, fuel consumption is not in the supportability scope and several additional aspects are missing. In fact, regulation aspects and maintenance strategies, for example, should be taken into account. Additionally, designing for future support would benefit from models that provide engineers with quantitative arguments regarding the relationship between design decisions and their operational and support-related impacts.